Problem: $\sum\limits_{n=1}^{3 }{{(n^2 - 1)}}=$
What is the question asking for? $\sum$ tells us to find the sum. The question is asking for the sum of the values of $n^2 - 1$ from $n = 1$ to $n = 3$. Evaluating $\begin{aligned} \sum\limits_{n=1}^{3 }{({n^2 - 1})}&= (1^2 - 1) + (2^2 - 1) + (3^2 - 1) \\\\ &= 0 + 3 + 8 \\\\ &= 11\end{aligned}$ The answer $\sum\limits_{n=1}^{3 }{({n^2 - 1})}=11$